Currently, thermoplastic tapes of a composite type material, such as a longitudinally reinforced thermoplastic resin, may be purchased in narrow widths typically of three to twelve inches. However, there are a variety of large scale thermoplastic processing technologies that require thermoplastic tapes having at least a sixty inch width. Machinery is needed to satisfactorily join narrow thermoplastic tapes together to generate a wide thermoplastic tape suitable for large scale thermoplastic technologies processing. Though apparatus has been proposed for simultaneously joining and laying down narrow tapes on fields used for sporting events, such is not suitable for achieving satisfactory seam structures usable in large scale thermoplastic technologies.
In order to obtain the necessary width, it has been the conventional practice to manually seam the individual tapes widths together. This is performed using hand held steaming irons. This antiquated method is time and labor intensive.
Hand seaming has not proven satisfactory because it requires an extensive amount of time to achieve the desired width. Hand seaming rates of less than 1 foot per minute are typical. Manual seaming is not reliable from a quality control standpoint as human variables inherent in manual manufacturing render the predictability of the material properties of the final tape impossible. Manual hand seaming permits fluctuation of variables affecting the final strength, namely, tape overlap, fiber orientation, appropriate pressure, heat application, and speed of operation.
The material characteristics of manually-made tape is difficult to predict because, among other things, inconsistent manual alignment of the individual tapes produces seam structures having nonuniform overlap. This is a problem because the angle and width of the overlap between adjacent narrow tapes is critical for predicting design strengths. Longitudinally reinforced thermoplastic tape is strongest in the lengthwise direction thus, the maximum strength of a seamed tape is attained when the individual narrow tapes are arranged in a precisely parallel relationship. Manual seaming methods and known machinery for seaming have not produced consistent seam overlap and alignment of the narrow thermoplastic tapes in a precisely parallel manner.
Manual seaming produces inconsistent seam quality due to erratic pressure and heat application. Consequently, inner fiber orientation is distorted causing a decrease in the final strength of the completed tape.
There are a variety of seam structures that cannot be readily produced with a manual seaming process and have not been attainable with known machine apparatus. In contrast, the present invention provides seam structures such as overlap, overlap mesh and butt. The present invention also provides for continuous or spot seaming.
Finally, hand seaming is inadequate as it renders the production of completed tape having widths greater than two feet virtually impossible because of the difficulty in manually reaching beyond two feet absent the use of a machine set up.
FIGS. 1A-1C show the conventional manual seaming procedure. In FIG. 1A individual plies of narrow tapes 12 and 12' are placed adjacent to one another and positioned to overlap one another in a consistent parallel fashion. As shown in FIG. 1B, heat and pressure are applied to the overlap region 14 of the individual narrow tapes 12 and 12' to melt fuse the individual tapes to one another in a seamed region 16. As shown in FIG. 1C, the manual seaming procedure requires an awkward final advancement step wherein either the tape material itself is moved to a subsequent tape section to be seamed or the seaming apparatus itself is extended to a subsequent tape section.
Conventional methods and apparatus, in contrast to the present invention, do not provide for the engineering of a particular seam structure and the maximization of the strength of the completed tape. The typical seaming methods and apparatus are not concerned with the final strength of the film. Considering the variables affecting the mechanical properties of the seamed tape, namely, the interrelationship of the kind of thermoplastic tape utilized, the variety of seam structures attainable, and the method of seaming, the present invention provides an apparatus and method for monitoring and controlling these variables to allow for the engineering of the final product. Additionally, the present invention provides an apparatus and method for joining thermoplastic tapes in an efficient and economic manner.
The present invention efficiently combines individual tapes of a composite material using a selected seam construction to produce a final tape of the desired width having superior strength. The present invention, unlike the conventional seaming apparatus and methods, allows the selection of a variety of seam constructions wherein the respective individual tapes are arranged and secured in a precisely and uniformly parallel manner.
Additional advantages of the present invention are set forth in the following detailed description, and will be obvious from the description or may be learned by practice of the invention. The advantages of the present invention will be realized and attained by means of the elements and combinations of elements present in the appended claims.